Charles b



(No Model.)

- G. E. SGRIBNER. MULTIPLE SWITCH BOARD FOR TELEPHONE EXCHANGES.

Patented June 30, 1885.

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NITED STATES PATENT rricn.

CHARLES E. SGRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE WESTERN ELECTRIC MANUFACTURING COMPANY, OF SAME PLACE.

MULTlPLE. SWITCH-BOARD FOR TELEPHONE-=EXCHANGES.

SPECIFICATION forming part of Letters Patent No. 321,391, dated June 30, 1885.

Application filed February 24,1881.

Renewed June 9. 1855. (No model.) Patented in England November 29, 1879, No. 4,903; in

France January 16, 1880, No. 134,596, and in Belgium January 28, 1880, No. 50,413.

To all whom it may concern:

Be it known that I, CHARLES SCRIBNER, of Chicago, Illinois, have discovered certain new and useful Improvements in Multiple Switch-Boards for Telephone-Exchanges, of which the following is a full, clear, concise,

' and exact description, reference being had to the accompanying drawings, forming a partof this specification.

A district telephone-exchange consists of a central office, with which the telephones of many subscribers are connected by independent lines, and where, upon request, any one subscriber may be put in communication with any other one of the subscribers. All the illdcpcndent iines, therefore, must be connected with a single switch-board. hen the numher of subscribers is large, and a single attendant cannot do the necessary switching, duplicate or multiple switch-boards are provided, all the wires being branched to each of the multiple boards, so that each board is complete in itself, and thus any two subscribers may be connected by an attendant at either one of the duplicate or multiple boards. An additional board is required for about every fifty new subscribers. The subscribers are apportioned so that a switchman at a given board answers only the calls of those assigned to his board. When a third subscriber wishes to communicate with one of two who are already connccted, great confusion often arises. This is wholly obviated by the use of my invention, which consists in so placing the cutouts or switches, and connecting them from one board to another, that the switchmen, re spectively, at the different boards may readily ascertain whether the wire of a subscriber called for is in use-that is, whether it is con nected with the wire of some other subscriber at any other board.

Figure l of the drawings represents two multiple switclrboards, A and B. Fig. 2 is a detailed View of the test-key and plug.

The telephone-lines are connected each with a switch or spring-jack on each switch-board, and thence back across the boards through other switches, and from the last board to ground. Thus the circuit of telephone-line m p of the may be traced to its switch a, and thence by wire 0 to its switch 1) of the second board. From the switch of the last board the circuit continues by wire Q back through switch 1', and thence by wire 8 to switch it, and thence through an annunciator to ground.

Switches are sometimes termed bolts. The portion of the circuit between the switch last board and the ground may be conveniently termed the test-circuit, and the switches included in the test-circuit may be termed test-keys.

In the drawingsI have shown but two switchboards, A and B. It is evident, however, that any number of switch-boards may be used, each being provided with a switch and a testkey for each line, so that any two subscribers may be connected upon either of the multiple boards.

The connection between any two subscribers is made by means of a pair ot plugs and cords, in the usual manner.

The test-key shown in Fig. 2 consists of the flat metallic spring a, fastened at one end rigidly to the board, and the metallic pin I), with which the spring is normally in contact. The portion of the pin between the board and the pin-head is surrounded by a sleeve, 0, of hard rubber. When the spring is carried away from contact with the pin-head, the contact between the spring and pin is broken.

The plug consists of the hard-rubber piece (I, provided with an opening, preferably through its center, for the conducting cord, which terminates in a metallic point, e, placed with in the cavity of the rubber piece (I. The point 0 should be so placed that when the rim f, or other projection of 11011-0O11dtl0l1l\78 substance, first touches the spring said point 6 will not be in contact with the pin-head. ()n pressing the projection f against the spring a, said spring is carried away from contact with pin 7), while metallic point e is brought into contactwith said pin 0.

By reference to Fig. 1 it will be seen that I have placed a test-key near each subscribers jackkniic switch on each of the multiple boards.

The subscribers telephone-lines are con nected, severally, with a switch and test-key on each board. For example, telephone-line m passes through switch a of board A, and thence by line 0 passes to the next board, B, and through switch 1), and thence by line Q to test-key 1*,and thence back to the first board, A, by line 8 to test-key t, and thence, in the usual manner, through an annunciator to ground.

By the use of my testkey the attendant is enabled to test and call by the same motion. Suppose attendant at board B wishes to con. nect any other of the subscribers switches with the switchp. Before making the connection the attendant must first see whether the switch a is not already connected with some other switch of board A, and, second, proceed to call up the subscriber wanted if he does not find line at in use. The testing and calling are done by simply pressing the plug it upon test-key r. The ground-wire s is taken off when the spring and pin of the test-key 1" are separated, and immediately the circuit of the batteryconnected with the flexible conducting-cord is completed through the bell by the contact formed between the metallic point e and the pin 1), as indicated in Fig. 2. If the line at is in use at switch a, the circuit of line 0 will be open at the eontactpoints of switch a, and the switehman at board B will get no response from his bell. He will therefore know that the line wanted is in use, and will notify the calling subscriber thereof; but in case the line m is not connected at switch a the bell at board B will respond, and a current will be sent along line at to the station of the subscriber connected with line m, thus calling him up. Vhen the subscriber thus summoned answers the call, the final communication may be made with switch 2 in the usual manner.

As thus described, it will be seen that there are two switches, or a pair of switches, on each board for each line. One of these switches is used for connecting the line of the pair with any other line. The other switch is included in the test-circuit, and is used primarily for testing to determine whether the line in whose circuit it is included is connected with any other line upon any of the other multiple boards.

It is a law of this system that when two lines are connected upon any one of the boards all the test-keys of each of the two connected lines are cut off. Therefore, when battery is connected to any one of the test-keys of a line which is in use, the circuit will be open at the tery through a signal-instrument to the line of a subscriber, whereby an attendant at any given board may test and signal at the same time.

CHARLES E. SCRIBNER.

\Vitnesses:

GEORGE P. BARTON, WALLAou L. DE \VoLr. 

